Exact solutions of modified GST cosmology (Q2741242)

With respect to some of its cosmological implications, a modification of the generalized scalar-tensor theory (GST) is considered. In modified GST, the cosmological term is a function not only of the scalar field \(\phi\) but, via \(\phi_i \phi^i\), also of its time derivative. One of the arguments in favor of this theory given by the authors is that a variable cosmological term and a scalar field are keywords for the present successes of present inflationary cosmology. Exact solutions are deduced for the scale factor, the scalar field and the cosmological term, where the latter evolves with a different dependence on time for each era of the universe. Qualitative considerations to the case of a flat universe provide physically reasonable results to the `cosmological constant' and the `flatness' problems.